Thanks for posting the RAW file ... I'll take you through how I would process this with a series of screen shots to see if that helps you.
Untitled-1.jpg
On opening the file in ACR the first thing is that as Rob says its got a very limited tonal range ... but its not over exposed - there are gaps at both ends of the histogram with no clipping
Untitled-2.jpg
Switching to the details tab, as a default ACR applies some capture sharpening 25/1.0/25/0 which I always accept - RAW files always need a bit of sharpening and this is a very modest amount
It also applies default noise reduction of luminance 0, colour 25 - this I do NOT accept as the amount of noise reduction required varied with ISO. I have a number of ISO dependant default noise profiles which I have built for my camera (Canon 40D) and I have ACR (or Lightroom) apply them automatically depending on the detected ISO of the image. For more information of how to do this see
<<<this thread>>>
Untitled-3.jpg 200% zoom
Resetting the noise reduction to 0/0 for a minute and zooming in we can see that there is both some colour & luminance some noise present in this image ... which is to be expected shooting at ISO 400.
The sensor on your 400D is not dis-similar to my 40D so starting from my ISO 0400 preset of 15/5 I found it was still a little bit noisy so edge the setting up to 23/8. Noise reduction is always a balance between removing noise and softening details ... I tend to err on the side of leaving a bit of noise if necessary rather than sacrificing detail.
Untitled-4.jpg 200% zoom
This would be my starting point before any exposure or black level adjustments etc. In the next post we'll look at how adjusting these setting affects the noise ... if at all